Sex-ratio biasing towards daughters among lower-ranking co-wives in Rwanda |
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Authors: | Thomas V Pollet Tim W Fawcett Abraham P Buunk Daniel Nettle |
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Institution: | 1.Department of Social Psychology, University of Groningen, Grote Kruisstraat II, 1 (Room 449), 9712TS Groningen, The Netherlands;2.Department of Theoretical Biology, University of Groningen, Groningen, The Netherlands;3.Department of Social Psychology, University of Groningen and Royal Netherlands Academy of Arts and Sciences, Groningen, The Netherlands;4.Centre for Behaviour and Evolution, Newcastle University, Newcastle-upon-Tyne, UK |
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Abstract: | There is considerable debate as to whether human females bias the sex ratio of their offspring as a function of their own condition. We apply the Trivers–Willard prediction—that mothers in poor condition will overproduce daughters—to a novel measure of condition, namely wife rank within a polygynous marriage. Using a large-scale sample of over 95 000 Rwandan mothers, we show that lower-ranking polygynous wives do indeed have significantly more daughters than higher-ranking polygynous wives and monogamously married women. This effect remains when controlling for potential confounds such as maternal age. We discuss these results in reference to previous work on sex-ratio adjustment in humans. |
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Keywords: | sex ratios human Rwanda polygyny Trivers– Willard hypothesis |
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